Jason had one heck of a day at the Open

GOLF: Jason Day has defied the afternoon winds to emerge as the hot Australian Open favourite.

Day is breathing down the neck of halfway leader Lucas Herbert after wowing fans with four straight back-nine birdies en route to a second-round three-under-par 68.

The former world No.1 climbed to eight-under for the championship, one behind Herbert, who capitalised on perfect morning scoring conditions with a sizzling 66.

First-round leader Cameron Davis cooled off with a one-over 72 but remained right in the mix in third spot at seven-under.

US PGA Tour stars Matt Jones, the 2015 champion, and Cameron Smith, runner-up last year to Jordan Spieth in a playoff, share fourth at four-under after respective second rounds of 67 and 69.

Former Australian Masters champion Nick Cullen (72) and veteran Richard Green (68) are at four-under, five off the pace.

Spieth faces an uphill battle retaining the Stonehaven Cup after failing to make any inroads on the leaders. His second-round 71 leaves the world No.2 and three-time major winner at one-under, eight shots adrift of Herbert.

While Day is undoubtedly in the box seat heading into the weekend, Herbert, who famously slept in the Carnarvon Golf Club car park during Open qualifying three years ago, collected six birdies before dropping his only shot of the day at the last.